1. Field of the Invention
This invention relates to an improved sanding pad for holding and supporting a sheet of coated abrasive sheet material during hand sanding operations.
2. Prior Art
Coated abrasive sheet materials are used in any of a wide variety of applications. Many applications require hand sanding where the user will grasp a coated abrasive sheet in his hand and apply it to the surface being treated. Such use has fostered numerous devices to assist in the holding of the coated abrasive sheet to avoid injuring the hand or fingers while maintaining the requisite position of and pressure on the coated abrasive sheet to its optimum effect. Improper positioning will cause uneven abrasion of the treated surface. Irregular pressure, such as caused by the fingers against the back side of the abrasive sheet in use, produces an irregular abraded surface.
Early holding devices used for this purpose were inflexible blocks of solid material such as wood over which the coated abrasive sheet was wrapped. While these devices were adequate for some purposes, they required some means of holding or attachment of the ends of the coated abrasive sheet while applying one face of the block against the surface being treated, thus not making the maximum efficient use of the paper since the ends are generally never exposed to the surface being treated. Various sanding blocks of this type employing means for grasping the ends of the abrasive sheet are known, for example as disclosed in U.S. Pat. Nos. 2,765,593 and 1,562,414. U.S. Pat. No. 1,562,414 discloses a similar hand block which requires at least a part of the block to be formed of a material which is somewhat flexible but sufficiently rigid to retain the ends of the abrasive sheet in slots cut therein.
There has been developed and marketed a self-adhering coated abrasive sheet material using pressure-sensitive adhesive coated on its back side so that it may be adhered directly to the working face of a sanding block. For the most part, this means of attachment assures exposure of the entire abrasive face of the abrasive sheet. Such abrasive sheets are disclosed in U.S. Pat. Nos. 2,485,295, 3,849,949 and 3,912,142. This type of abrasive sheet has been extremely useful in conjunction with hard sanding blocks such as the types mentioned above and for rotatable disc sanding heads.
While the rigid sanding blocks are useful for sanding flat areas or areas with moderate surface variation, such as curved parts with a large radius of curvature, great quantities of abrasive sheet material are still used on complex surfaces, such as carved patterns, curved parts having a smaller radius of curvature and the like, without a pad. There has been no acceptable sanding pad, prior to the present invention, which is sufficiently conformable to be used to sand complex surfaces and particularly which can use the new type of adhesive-coated abrasive sheet material.
There are numerous patents showing flexible abrasive devices in the form of gloves which are coated on the palm surface with abrasive material. Examples of these are shown in U.S. Pat. Nos. 203,959, 1,346,683, 2,459,985 and 4,038,787. While such devices are adequate for some purposes, they are not adequate for use in situations where uniform sanding pressure is required because of the non-uniformity of the pressure applied by the various parts of the hand. Additionally, because of their irregular surfaces, gloves do not provide an adequate surface upon which the new pressure-sensitive adhesive-coated abrasives may be applied. The gloves are also generally over-sized to fit a wide variety of hand sizes; thus motion during abrasion causes the fingers and palm to move in the glove with respect to the areas of abrasive, providing erratic abrading and often discomfort to the user.